The present application relates generally to methods of interfacing remote units with a central computer, and more particularly to methods of interfacing remote units with a central microprocessor in a home appliance.
It is becoming increasingly common for microprocessors to be used in electric ranges, microwave ovens, and other home appliances. Since microprocessors malfunction from time to time, it is necessary to have an inexpensive and simple means for diagnosing problems arising in them. One means of doing so would be to provide extensive diagnostic circuits in the microprocessor itself. These circuits would continuously or periodically check the operation of the microprocessor and signal the user when a malfunction was discovered. The inclusion of such a large number of diagnostic circuits, however, would significantly increase the cost of the appliance.
It is accordingly preferred to minimize the number of diagnostic circuits in the appliance itself and to provide a separate hand-held module containing all of the necessary diagnostic circuits for the appliance manufacturer's field service representative to examine the appliance and determine the problem.
To date, hand-held diagnostic modules have been complex and expensive, at least in part because of the problems of interfacing them with the microprocessor in the appliance.
In addition, a manufacturer often desires to modify the capabilities of a home appliance. Modification of the appliance's circuitry, however, is quite expensive. It is preferable to add the new circuitry in a separate module that can be simply attached to the original circuitry without modifying the latter. A simple and economical solution of the interfacing problem could be advantageously applied as well to this problem.